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Old 03-26-2021, 08:09 PM   #1
Stubaru91
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Default Bad cat? Bad sensor? Bad gas?

I have an 07 Impreza 115k, (was for sale on here actually) that is throwing a P2096 CEL. Car is running fine, maybe a tad low on power but maybe Iím biased comparing it to my new STi.

A week or 2 prior to the CEL you could really smell the exhaust strongly, not fuel but exhaust, in and around the vehicle. I hear the cats on these cars are known to fail easily but with the symptom of the smell Iím not sure if would suggest it is the cat or a bad sensor.
I cleared the code and the car ran for almost 2 tanks of gas (~700 miles) before it threw it again so that also has me scratching my head, thatís a hell of a long time for a sensor issue IMO.

I also should mention that Iíve been running E88 (NOT E85) since itís cheaper so I wonder if that could possibly have anything to do with it.

Iím trying to decide if I should invest in a cat/sensors for a car I paid $1800 for that has either piston slap or rising knock or if I should just get brakes on it so itís safe and drive it till it explodes.

Thanks!!
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Old 03-26-2021, 10:50 PM   #2
serrilion
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I would check you Vac lines make sure you don't have a leak

Change the fuel filter as thats simple enough to make sure your getting enough fuel, who knows when it was last changed, could be causing a fuel shortage

A bad manifold to cat gasket can cause exhaust fumes to come in threw your fresh intake vent as its right above your manifold in your windshield cowling. Having a leak can cause the sensor to read incorrectly as the cat is not getting the proper air flow and can be indicating a lean mixture.

Hope this was of some help
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Old 03-27-2021, 06:23 AM   #3
Stubaru91
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Quote:
Originally Posted by serrilion View Post
I would check you Vac lines make sure you don't have a leak

Change the fuel filter as thats simple enough to make sure your getting enough fuel, who knows when it was last changed, could be causing a fuel shortage

A bad manifold to cat gasket can cause exhaust fumes to come in threw your fresh intake vent as its right above your manifold in your windshield cowling. Having a leak can cause the sensor to read incorrectly as the cat is not getting the proper air flow and can be indicating a lean mixture.

Hope this was of some help


So while driving with the window down, again you can smell the exhaust as well. Does that point me toward that bad gasket?
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Old 03-27-2021, 03:09 PM   #4
serrilion
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Quote:
Originally Posted by Stubaru91 View Post
So while driving with the window down, again you can smell the exhaust as well. Does that point me toward that bad gasket?

Could be, you would notice the car being louder while accelerating. Could be manifold gaskets as well or the heat shields on the exhaust like to hide spots were its rotted threw. Again it would be much louder.



One trick is to cold start the car with someone wearing a glove and holding hand over the muffle exhaust exit and looking under neath the car for a leak. You would see the condensation burn off coming out of the leaked area


Just an idea

Last edited by serrilion; 03-27-2021 at 03:10 PM. Reason: clarification
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Old 03-28-2021, 12:05 PM   #5
Stubaru91
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Quote:
Originally Posted by serrilion View Post
Could be, you would notice the car being louder while accelerating. Could be manifold gaskets as well or the heat shields on the exhaust like to hide spots were its rotted threw. Again it would be much louder.



One trick is to cold start the car with someone wearing a glove and holding hand over the muffle exhaust exit and looking under neath the car for a leak. You would see the condensation burn off coming out of the leaked area


Just an idea


Car doesnít sound much louder to me unless Iím mistaking what I think is piston slap or a rising knock as an exhaust leak. Iím not really convinced the knock is serious or even an actual. Car gets a lot of miles daily and never has gotten worse since Iíve had it. Might go change the oil today. If my brother is home Iíll have him do the exhaust trick.
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Old 03-28-2021, 01:30 PM   #6
Elbert Bass
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You identify the car as an Impreza. Normally aspirated or a WRX/STI that is tuned for E85?

If you are running a stock N/A car or a car not tuned for E85 on anything over E15 you will see that code.
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Old 03-29-2021, 08:06 PM   #7
Stubaru91
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Originally Posted by Elbert Bass View Post
You identify the car as an Impreza. Normally aspirated or a WRX/STI that is tuned for E85?

If you are running a stock N/A car or a car not tuned for E85 on anything over E15 you will see that code.


Not running E85. Iím running E88. 88 octane, 15% Ethanol.
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Old 03-30-2021, 07:51 AM   #8
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Originally Posted by Stubaru91 View Post
Not running E85. I'm running E88. 88 octane, 15% Ethanol.
Oh, I had not heard of that before - the E nomenclature made me think it was 88% ethanol. Nothing like the marketing department to muddy waters...
I would switch back for a few tanks to see what happens. Subaru tells their techs at Suby school that Subaru of that era is not designed to run on any ethanol additive fuels and that should be considered when having fuel trim issues. I have never seen issues with Subarus unless the fuel was bad or was over 15%

I would definitely perform a alcohol content test to verify it's only 15%.
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Old 03-30-2021, 10:54 AM   #9
Stubaru91
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Originally Posted by Elbert Bass View Post
Oh, I had not heard of that before - the E nomenclature made me think it was 88% ethanol. Nothing like the marketing department to muddy waters...
I would switch back for a few tanks to see what happens. Subaru tells their techs at Suby school that Subaru of that era is not designed to run on any ethanol additive fuels and that should be considered when having fuel trim issues. I have never seen issues with Subarus unless the fuel was bad or was over 15%

I would definitely perform a alcohol content test to verify it's only 15%.


Thatís why I asked in the subject if itís maybe bad gas. Iím a fan of running it because itís 20 cents cheaper than 87, I get the same economy, and my commute is 36 miles one way. Trying to keep the miles off my STi for as long as possible.
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Old 03-30-2021, 06:34 PM   #10
Elbert Bass
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Quote:
Originally Posted by Stubaru91 View Post
Thatís why I asked in the subject if itís maybe bad gas. Iím a fan of running it because itís 20 cents cheaper than 87, I get the same economy, and my commute is 36 miles one way. Trying to keep the miles off my STi for as long as possible.
Sure could be, the only way to know is use "regular" 10% gas for a while and see what happens.
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Old 03-30-2021, 09:13 PM   #11
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Originally Posted by Elbert Bass View Post
Sure could be, the only way to know is use "regular" 10% gas for a while and see what happens.


I talked to the mechanic on my mail route today about it and explained the situation. Heís a well educated guy, lots of certifications and made a very good career off his knowledge and talent.

He looked me straight in the eyes and told me to absolutely not run e88 in it. He suggested 89 could possibly help but thatís what was in the car for the first time it threw the light. He then gave me reasons why that could have been and then circled back and said do 87 in next fill up and clear the code. I also do run a big brand/lower-ish quality fuel in it because itís close by, has e88 pumps, and is cheaper. But Iíll go to my local Exxon and throw 87 in it and go from there.
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Old 04-01-2021, 07:22 PM   #12
serrilion
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Quote:
Originally Posted by Stubaru91 View Post
I talked to the mechanic on my mail route today about it and explained the situation. Heís a well educated guy, lots of certifications and made a very good career off his knowledge and talent.

He looked me straight in the eyes and told me to absolutely not run e88 in it. He suggested 89 could possibly help but thatís what was in the car for the first time it threw the light. He then gave me reasons why that could have been and then circled back and said do 87 in next fill up and clear the code. I also do run a big brand/lower-ish quality fuel in it because itís close by, has e88 pumps, and is cheaper. But Iíll go to my local Exxon and throw 87 in it and go from there.

Sounds like a good plan, I honestly mis read passed the part about bad gas sorry about that!
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Old 04-02-2021, 07:49 PM   #13
Stubaru91
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Originally Posted by serrilion View Post
Sounds like a good plan, I honestly mis read passed the part about bad gas sorry about that!


Took it as far to empty as I was comfortable with, filled up on Sunoco 87 and then stopped at a friends and cleared the code. Stay tuned!
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Old 04-08-2021, 07:34 PM   #14
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Originally Posted by serrilion View Post
Sounds like a good plan, I honestly mis read passed the part about bad gas sorry about that!


Check engine light is back . The STi is getting an AOS install this weekend. Next oil change for the Impreza Iím going to have the mechanic on my mail route do it and see if he can take a gander. The sensor directly below the passenger side headlight on the exhaust...near the heat shield, that all looks very ďsootyĒ is that a common place of failure for these exhausts?
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Old 04-08-2021, 08:20 PM   #15
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You mentioned that you smelled exhaust fumes... An exhaust leak up-stream of the sensor could cause that code. I've also seen A/F sensors cause that code, too. Also, pull the MAF out of the intake and see if the sensor is dirty or has debris on it.
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Old 04-08-2021, 09:41 PM   #16
Stubaru91
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Originally Posted by CaptainSlowbaru View Post
You mentioned that you smelled exhaust fumes... An exhaust leak up-stream of the sensor could cause that code. I've also seen A/F sensors cause that code, too. Also, pull the MAF out of the intake and see if the sensor is dirty or has debris on it.


I can check the MAF tomorrow. Canít they be cleaned with something?
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Old 04-11-2021, 08:55 PM   #17
serrilion
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I can check the MAF tomorrow. Canít they be cleaned with something?

Yes there is a mass airflow spray you can use on them to clean them. Depending how dirty they are, it should clean it up pretty well.
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Old 04-19-2021, 08:25 PM   #18
Stubaru91
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Yes there is a mass airflow spray you can use on them to clean them. Depending how dirty they are, it should clean it up pretty well.


I havenít gotten to it yet. Still sending the car though. Driving fine. Stopping at a friends I think a day this week where weíll get a good reading from a snap on scanner and weíll clean the MAF real quick.
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